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The Promise And Pitfalls of Bioplastic

5 minute read
Kristina Dell

Regular, petroleum-based plastic doesn’t biodegrade. But this year’s crop of Earth Day — inspired ads shows plant-based plastics doing just that: an empty SunChips bag fading into the soil, a Paper Mate pen dissolving underground. Although the visuals suggest that these items simply disintegrate (Goodbye, landfill!), the reality is more complicated. Take the SunChips bag. It needs to go in a compost bin; the packaging is clear about that. Likewise, Paper Mate notes that the pen’s outer casing will break down if buried in a backyard but that its innards should go in the garbage. Forget to separate them, and the outer part won’t biodegrade in a landfill.

Bioplastics could be really good for the environment — the manufacturing process produces fewer greenhouse-gas emissions than that for petroleum-based plastics, and these biomaterials don’t contain an allegedly hormone-disrupting chemical, bisphenol A (BPA), that some regular plastics do. But is society green enough to use bioplastics? Many of us still don’t recycle all our bottles and cans, and now companies are expecting us to start composting?

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Bioplastics have been around for decades — Henry Ford made automotive parts out of corn and soybean oils for the Model T — and interest in these materials has tended to fluctuate with the price of oil. Of the two promising new varieties of bioplastic, one type — dubbed polylactic acid, or PLA — is clear in color and costs manufacturers about 20% more to use than petroleum-based plastic. The other — called polyhydroxyalkanoate, or PHA — biodegrades more easily but is more than double the price of regular plastic. Both bioplastics are made of fermented corn sugar, and both come with a major benefit: if disposed of properly, they won’t stick around in landfills for thousands of years.

But that’s a big if. The PLA resins that biodegrade when composted are showing up in more and more consumer products. For example, NatureWorks makes polymers that are now in SunChips bags, water bottles in some government cafeterias and new Coca-Cola fountain-soda cups. (There are also nonbiodegradable versions in Canon copiers and Toyota Prius floor mats.) Other firms are trying to make PLA using switchgrass, potatoes and algae.

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PHA is more expensive, but it can handle higher temperatures and is the only bioplastic that will decompose in soil or waterways. (No more floating garbage.) “Disposable, one-use plastics that biodegrade seem the most beneficial for society,” says Oliver Peoples, co-founder of and chief scientific officer at Metabolix, whose Mirel PHA is in Paper Mate pens and Target gift cards. “A regular plastic fork stays around for hundreds of years.”

But if a biodegradable fork ends up in an airtight landfill, it will most likely remain intact, just like regular plastic. However, should moisture seep in, bioplastics could anaerobically degrade and give off methane, a powerful greenhouse gas. “When you dispose of biodegradable plastic, it decomposes into an air-pollution problem,” says Tillman Gerngross, an engineering professor at Dartmouth, who used to work for Metabolix and is now one of PHA’s main critics. (NatureWorks says third-party tests revealed that its PLA stayed inert.) But discarded bioplastic is not the only potential methane emitter in landfills. Kitchen scraps and yard waste emit the gas, which is one reason many garbage dumps have started capturing methane output and using it for energy.

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The market for bioplastics is still relatively small, and until it gets bigger, eco-savvy consumers may have trouble dropping their bioplastics off at recycling facilities or composting centers. PLA is easy enough to recycle, but it can’t be mixed with the current recycling stream. And smaller companies have yet to add sorting mechanisms like infrared technology that can separate clear bioplastic bottles from the regular, petroleum-based kind. Meanwhile, some composting centers have a blanket policy of discarding all plastic. “I direct pickers to take out plastic, which they can’t distinguish from bioplastic,” says Will Bakx, co-owner of and soil scientist at Sonoma Compost, a composting facility in Petaluma, Calif.

Many of the disposal issues could be resolved if manufacturers follow Bakx’s suggestion and adopt a uniform color to identify bioplastic resins. Until then, Naturally Iowa is selling its PLA water bottles only in places like hotels and cafeterias, like the ones used by Congress and the U.S. Department of Agriculture, where the company can pick up and recycle the plastic waste. Says CEO Bill Horner: “We want to touch the bottle after it’s used and know where it is going to go.”

Breaking our petroleum addiction won’t be easy. But the more pain we feel at the pump — gas prices are expected to go back up to $3 a gal. (80¢ per L) this summer — the more we’ll be willing to adapt. For now, many SunChips purchasers are complaining not about the lack of industrial composting sites but about how much noise the new bag makes. “I tried to sneak some SunChips at night, and I woke my wife up,” says Bob O’Connell, a compliance officer in New Port Richey, Fla. “That’s how loud the bag is.” Ah, priorities. For many, green still takes a backseat to convenience.

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